Refrigerated reach-in display compartment

ABSTRACT

A compartment having one open side and inner walls extending to opposite edges of said open side around the area to be refrigerated which inner walls define the walls of a first conduit for conducting refrigerated air from an inner inlet along one of said opposite edges of said open side to an inner discharge nozzle along the edge opposite thereto for forming a curtain of primary or refrigerated air across said open side between said nozzle and said inlet.

@nited States Patent [191 Simons et al.

[ Nov. 13, 1973 REFRIGERATED REACH-IN DISPLAY COMPARTMENT Inventors:Edward Widman Simons, Mill Valley; Edward Warren Simons, San Francisco,both of Calif.

Assignee: Dualjet Corporation, Tiburon,

Calif.

Filed: May 17, 1972 Appl. No.: 254,225

Related U.S. Application Data Continuation-impart of Ser. No. 214,702,Jan. 3, 1972, abandoned.

U.S. Cl 62/89, 98/36, 62/93, 62/186, 62/256 Int. Cl. F25d 17/06 Field ofSearch 62/89, 93, 186, 256; 98/36 References Cited UNITED STATES PATENTS5/1964 Hagen 62/256 3,147,602 9/1964 Beekwith 62/256 3,287,929 11/1966Beekwith 62/256 3,304,736 2/1967 Brennon 62/256 3,365,908 1/1968MacMaster... 62/256 3,394,755 7/1968 Morrison 98/36 3,403,525 10/1968Beckwith 62/256 3,063,252 11/1962 Lamb..... 62/256 3,063,256 11/1962Lamb 62/256 Primary ExaminerWilliam J. Wye Attorney-Mark Mohler et al.

[57] ABSTRACT A compartment having one open side and inner wallsextending to opposite edges of said open side around the area to berefrigerated which inner walls define the walls of a first conduit forconducting refrigerated air from an inner inlet along one of saidopposite edges of said open side to an inner discharge nozzle along theedge opposite thereto for forming a curtain of primary or refrigeratedair across said open side between said nozzle and said inlet.

18 Claims, 21 Drawing Figures PATENTEDHUV 13 I975 3.771, 323

SHEET u or 5 FIG.8 FIGS A 7' Ln PATENTEnuuv 131915 sum 5 or 5 FIGJQREFRIGERATED REACH-IN DISPLAY COMPARTMENT A second conduit outwardly ofsaid first conduit and heat insulated therefrom by intermediate wallsconducts unrefrigerated or guard air around the area bounded by saidinner walls from an outer inlet outwardly of said inner inlet andadjacent to the latter to an outer nozzle outwardly of and along saidinner nozzle to discharge an outer curtain of guard air of highertemperature than said primary air across said open side.

Altitude-compensating dampers in said conduits are automaticallyactuatable by changes in the density of the ambient air at differentelevations to maintain air distribution pressure within said conduits atelevations substantially above sea level.

Velocity-maintaining dampers within said conduits are automaticallyactuatable upon and by reason of the occurrence of unequal velocities ofair within said first and second conduits for movement to differentpositions to reestablish the air velocities in the conduitsapproximately equal.

A refrigerated uninsulated heat transfer member in communication withthe air within both conduits is movable to different positions acrossthe reflective space within said first conduit to dehumidify said guardair.

Structure is also provided for moving the air within said conduitswhereby a single air mover may be used in each compartment, and alsostructure is provided for drainage of melted ice on the inner ceilingwall of the area bounded by said inner walls upon defrosting.

BACKGROUND OF THE INVENTION This is a continuation-in-part of US. Pat.application Ser. No. 214,702 filed Jan. 3, 1972, now abandoned.

The present invention relates to improvements in the type ofrefrigeration systems in which one of the sides of the area to berefrigerated is open.

Systems of this general type are shown in US. Pat. Nos. 2,862,369 and3,397,631 of Dec. 2, 1958 and Aug 20, 1968, respectively, US. Pat. No.3,128,609 of Apr. 14, 1964 to S. Beckwith et al. and Hagen et 211.3,134,243 of May 26, 1964.

In these installations in which an inner curtain of refrigerated air,hereinafter referred to as a curtain of primary air, and an adjoiningcurtain of higher temperature, hereinafter referred to as a curtain ofguard air, are projected across the open side of the compartment, it hasbeen found that the air distribution along the discharge nozzles arearranged for lower elevations, is erratic and irregular at substantiallyhigher elevations where air density is lower.

Also in such installations where the air of the guard curtain is ambientair of excessively high humidity frost-clogging of the cooling coils forcooling the primary air noticeably increases the defrostingrequirements.

Furthermore, in the multiple-air-curtain installations employing primaryand guard air, the velocity of the primary air becomes progressivelyslower than the velocity of the guard air following each defrosting ofthe cooling coils, whereas the velocity should preferably besubstantially the same at all times to produce optimum results.

SUMMARY OF THE INVENTION Generally the objects of the present inventionare the provision of method and means in systems of the type hereinabovementioned, for overcoming the objections above-described and others.

One specific object of the invention is the provision of a method andmeans in a system of the type hereinabove described for providinguniform air distribution at the discharge nozzles at elevations whereheretofore the distribution has been irregular and unsatisfactory due tothe change in pressure characteristics of flow at higher elevations.

Another object is to provide a method and means in a cooling systememploying separate conduits for the primary and guard air for thecurtain, for dehumidifying the guard air before it reaches the curtainfor reducing the high requirements for defrosting the cooling coils.

An added object of the present invention is the provision of means formaintaining equal velocities of the air to the discharge nozzles or tomaintain the movement of the air at predetermined different velocities.

A still further object is the provision of means in a multiple conduit,multiple air-curtain arrangement in a compartment cooling structure ofthe type described, for effecting movement of the air in the conduits ofa series of sections or compartments, in a more efficient manner thanheretofore.

In addition to the foregoing, a still further object of the invention isthe provision means for the removal of ice and moisture that may occuron the ceiling or in the upper portion of the compartment beingrefrigerated.

Other objects and advantages will appear in the description anddrawings.

DESCRIPTION OF DRAWINGS FIG. 1 is a simplified, perspective view of acabinet having two compartments, the shelves therein being omitted.

FIG. 2 is an enlarged, vertical cross-sectional view through one of thecompartments in a cabinet.

FIG. 3 is a schematic view of the velocity control unit indicated inFIG. 2.

FIG. 4 is a fragmentary enlarged cross-sectional view of a modificationof a portion of the structure shown in FIG. 2.

FIG. 5 is a semi-diagrammatic fragmentary sectional view of amodification on the blower system only of FIG. 2.

FIG. 6 is an enlarged fragmentary cross-sectional view of a portion ofFIG. 5.

FIG. 7 is a diagrammatic view of a modification of the arrangement ofFIG. 5 in a pair of sections as viewed at a right angle to FIG. 5.

FIG. 8 is a semi-diagrammatic, enlarged crosssectional view along line8-8 of FIG. 7.

FIG. 9 is a semi-diagrammatic view similar to FIG. 8 as viewed alongline 9-9 of FIG. 7.

FIG. 10 is a diagrammatic view of one section, similar to FIG. 7, inwhich one blower is driven in an opposite direction to the other by asingle motor.

FIG. 1 l is a diagrammatic view at line 11-11 of FIG.

FIG. 12 is a diagrammatic view at line l2-l2 of FIG. 10.

FIG. 13 is a diagrammatic view similar to FIG. in which separate motorsdrive the respective blowers in one section oppositely.

FIG. 14 is a semi-diagrammatic, cross-sectional view through onecompartment, showing a modification in which a single blower of thepropeller type circulates the air for a pair of contiguous layers ofprimary and guard air.

FIG. is a semi-diagrammatic, cross-sectional view of a modification ofthe structure shown in FIG. 14.

FIGS. 16-18 each diagrammatically shows a different modification of theintermediate conduit wall at opposite sides of the blower or face shownin FIG. 15.

FIG. 19 is an enlarged, fragmentary cross-sectional view of a modifiedportion of FIG. 2.

FIG. is a fragmentary elevational view of the structure shown in FIG.19.

FIG. 21 is an elevational view of a further modification of thestructure shown in FIGS. 19 and 20.

DESCRIPTION OF THE INVENTION The compartment illustrated may be onecompartment having opposite end walls, which are normally insulated, orit may be one of several in a row, in which case the framework withinthe cabinet may provide one set of air conduits for each compartment.FIG. 1 shows a pair of compartments with a partition separating them.

The details of construction, such as the provision of structuralreinforcing and spacing members between walls defining the air conduitsand other structural features are well known to those skilled in theart, are simplified or omitted in the interest of clarity.

FIG. 2 is a simplified semi-schematic, vertical crosssectional viewtaken transversely through a compartment of FIG. 1 having an inner wallgenerally designated I. Said wall 1 comprises a generallyhorizontallyextending inner ceiling or upper wall 2, a verticallyextending inner rear wall 3 and a horizontally extending inner bottomwall 4. The front side of the compartment is open or is provided with anopening through which access to the interior of the compartment is had.

Walls 2, 3, 4 are not heat insulated, and are of material such as metal,having good heat conducting properties.

An intermediate wall generally designated 5 is spaced outwardly of theinner wall 1, and is insulated against transfer of heat. Said wall 5comprises an upper generally horizontally extending wall 6 that may beparallel with wall 1 and in spaced, opposed relation thereto, a

vertically extending wall 7 in parallel spaced opposed relation to wall3, and a generally horizontally extending lower wall 8 in spaced opposedrelation to wall 4.

The outer wall of the compartment, generally designated 9, is spacedoutwardly of the intermediate wall 5, is insulated against transfer ofheat, which wall includes an upper wall 10 in spaced opposed relation towall 6, a vertically extending rear wall 11 in spaced opposed relationto wall 7, and a bottom wall 12 in spaced, opposed relation to wall 8.

The primary and guard air conduits extending around a cabinet from theopen side may be divided by a frame member 13 (FIG. I) so that onesection of the conduits is at one side of the partition and anothersection at the other side. There may be any number of such sections in acabinet, according to the length of the latter and the number of suchframe members. Usually the distance between the ends of each section isapproximately 4 to 12 feet, and the interior of the cabinet may includea partial or full partition 13 at each member 13. Thus the wordcompartment will be used to identify the area within a cabinet acrossone open side of which a pair of air curtains from a pair of dischargenozzles extend.

Walls 1 and 5 define opposite sides of an inner air conduit generallydesignated 15, and walls 5, 9 define opposite sides of an outer conduitgenerally designated 16.

The upper forward end of conduit or passageway 15 communicates with ahorizontally elongated, downwardly directed discharge nozzle 17, whilethe upper forward end of conduit or passageway 16 communicates with acorrespondingly elongated downwardly directed discharge nozzle 18. Thesenozzles extend substantially from end-to-end of each compartment and areparallel, with nozzle 18 alongside but slightly above nozzle 17. Saidnozzles are of the type shown and described in U. S. Letters Patent3,143,952 of Aug. 11, 1964 in which each nozzle comprises a plurality ofparallel adjacent passagewayshThe passageways of nozzles 17, 18 extendconvergently downwardly relative to each other to respectively form aninner curtain l9 and an outer curtain 20 obliquely meeting adjacent tothe nozzles whereby the curtains will move contiguously downwardly insubstantially parallel paths to enter inlets 21, 22 at the lower forwardends of conduits 15, 16.

The lower end of conduit 15 communicates with inlet 21, which isupwardly directed to receive the air of curtain 19 and the lower forwardend of conduit 16 communicates with the inlet 22, which is upwardlydirected to receive the air of curtain 20. Said inlets extend fromend-to-end of the compartment, the nozzles 17, 18 defining the upperedge or side of the open side of the compartment, and inlets 21, 22defining the lower edge or side of said open side.

Shelves, indicated in dot-dash lines, are normally provided within thecompartment for supporting the products to be positioned therein. Suchshelves do not project sufficiently far from the rear wall 3 to disturbthe air curtains 19, 20.

Cooling coils 23 are positioned within the portion of conduit 15 that isbelow the bottom wall 4.

The air that is moved through the conduit 15 from the inlet anddischarged from the nozzle 17 has been called primary air, beingconditioned or refrigerated, while the air moved through conduit 16 hasbeen called guard air, and the curtain 20 a guard curtain, as it isinterposed between the atmospheric outside air and the curtain 19. It iscommon at times to provide means for forming an additional guard curtainoutside the curtain 20, particularly where compartments may be atopposite sides of an aisle with their open sides facing each other.Insofaras the present invention is concerned the guard curtain and guardair is the curtain that is adjacent to the primary air. Whether one ormore guard curtains is or are provided is immaterial.

The word width where used with respect to either conduit means thehorizontal dimension in a section longitudinally of the compartment,while the word depth is the horizontal dimension at a right angle to thewidth.

As seen in FIG. 2 the propeller type air movers 24, 25 are respectivelyshown in the portions of conduits 15, 16 below the bottom wall 8.

A portion of the intermediate wall 7 that is between conduits 15, 16comprises a dehumidifying plate 28 of uninsulated heat conductivematerial. This plate is parallel with wall 3 and is in alignment with anopening in the intermediate rear wall 7, forming a reflective space. Aflexible diaphragm 29 around the edges of the plate connects with saidwall 7 and closes the opening to leakage of air from one of the conduitsto the other.

A plurality of bearings 30 (FIG. 2) secured to the inner wall 3 supportsrods 31 that, in turn, are secured to plate 28, thereby carrying plate28. Plate 28 may be moved to different positions toward or away fromwall 3 by manually pushing or pulling rods 31 from within thecompartment to increase or decrease the reflective space between wall 3and plate 28. A set screw 32 threadedly extending through each bearing30 will secure each rod 31, and consequently plate 28, in adjustedposition.

Straight, vertically disposed, horizontally spaced heat conducting fins33 or heat conducting pins 34 on the plate 28 spaced between adjacentpairs of fins 33 project into conduit 16.

By moving the plate 28 toward inner wall 3 the reflective space betweenthe plate and wall 3 will be decreased. As this distance is decreased,the fins 33 or pins 34 will become colder, with correspondingdehumidiflcation of the air in conduit 16. The plate 28 may be fixed inthe adjusted position for obtaining the desired dehumidification of theair in the conduit 16. The result is a decrease in the frosting of coils23, hence a decrease in the defrosting requirement, due to a reductionin the humidity of air in conduit 15 resulting from some air in curtain20 becoming entrailed with the air in curtain 19.

One or more dehumidifying plates may be employed in wall 7, which platesmay be of the size found to be most effective for the humidityconditions and the size of the conduits.

When display cases of the type herein described, arranged to operateefficiently at or about sea level, are operated at several thousand feetelevation, the velocity of the jets at various points along the nozzleshave been observed to be erratic and irregular. Such eccentricitiescause uneven maintenance of temperature in the display case, whether itis of the type having two or more contigious air curtains for ice creamand frozen foods or that having a single air curtain as is commonlyemployed for meat and delicatessen products.

It is believed that this results from a loss of distribution pressure,i.e., the pressure in the air curtain system is below the minimumrequired to assure even distribution of air velocity at all points alongthe jet nozzles because the air is less dense at the higher elevation.This problem may be solved by increasing the air flow in the curtainconduits at higher altitudes so as to increase the pressure in thesystem by the use of an altitudecompensating damper. Although the damperwill first be described and is shown in conduit 15, it may be similarlyutilized in conduit 16.

A damper plate 37 (FIG. 2) extends across the width of the compartmentand may be positioned for movement projecting into conduit 15. Theintermediate wall 7 may be formed with a recess 38 to receive said platewhile a flexible expandable and contractible diaphragm 39 extends aroundthe edges of the plate connecting it with the wall 7 to prevent leakageof air through opening 38.

A plurality of sets of rods 40 secured at one of their ends to plate 37slidably extend into the recess 38 and through the rear wall 11. Saidrods support the plate 37 for movement to different positions across theconduit 15. The rearwardly projecting ends of rods 40 are connected witha cross frame member 41, and between said member and wall 11 is aclosed, horizontally expandable and contractible, sealed, closed bellows42 enclosing air or gas.

A pair of legs 43 between rods 40 and at opposite sides of bellows 42are rigid on wall 11 at one of their ends, and a cross bar 44 connectstheir opposite outer ends. Cross member 41 has bearings 45 through whichlegs 43 extend, hence member 44 slidably support legs 40.

A rod 46, secured at one end to cross member 41 extends through abearing 47 and projects outwardly of cross bar 44. g

A spring 48 around rod 46 is secured at its ends to cross member 41 andcross bar 44 and normally, at approximately sea level, and up to apredetermined, relatively low elevation the spring 48 will not be understress and will yieldably maintain the plate 37 projecting into conduit15 to restrict the flow of air through the latter. In effect damper 37throttles conduit 15 at lower elevations.

At higher elevations, above said predetermined elevation, the expansionof air or gas contained within the bellows will result in automaticallymoving the plate 37 toward the opening or recess in the intermediatewall 7 thereby withdrawing it from and resulting in an in-' crease inthe quantity of air flow in conduit 15. The increased circulation causesan increase in pressure sufficient to maintian the distribution pressureto preserve even velocity distribution along the nozzle.

The provision of a set screw 49 in bearing 47 for engaging the rod 46would enable releasably fixing the plate 37 stationary within theconduit 15 at any altitude, since the head of rod 46 is accessible formanually moving the plate to any desired position.

The plate 37 and bellows 42 or their equivalent constitutes a barometricdamper responsive to variations in the density of the air at differentaltitudes to control the volume flow of air in the conduit and maintainsufficient distribution pressure. I

In the modified form of the invention as seen in FIGS.

19, 20, a barometric control damper is positioned in conduit 15 and asimilar damper 176 is positioned in conduit 16. In the positions shownin FIG. 19 said dampers restrict the volumetric capacities of bothconduits, at lower elevations, and each damper may extend substantiallythe full width of each compartment.

Walls 177, 178, which substantially correspond to walls 7, 11 arerecessed at 179, 180 for retraction of dampers 175, 176 for increasingthe volumetric capacities of conduits 15, 16 and thereby modifying thedistrisecured to and support damper 175. Sleeves 182 are secured todamper 176 at their inner ends, and are adjustably secured at theirouter ends to rods 181 by set screws 184.

A head on the outer end of each sleeve is adapted to be manually graspedfor adjusting the position of damper 176 relative to damper 175 andconduit 16.

Movement of the cross member 183 away from wall 178 will result insimultaneous movement of dampers 175, 176 in conduits 15, 16 to increasethe volumetric capacities of the conduits 15, 16.

Conventional packing glands may be provided on rods 181 and sleeves 182to preclude leakage of air through the openings in walls 177, 178 whilepermitting reciprocable movement of the rods 181 and sleeves 182.

An expandable and contractible, sealed bellows 185, similar to bellows42, encloses gas and is positioned between wall 178 and cross member183.

A pair of legs 186 at opposite sides of each bellows are rigid on wall178 at one of their ends, and a cross bar 187 connects their oppositeends. Cross member 183 has bearings 188 through which legs 186 extend,and a rod 189 secured at one end to cross member 183 extends through abearing 190 centrally between the ends of cross bar 187.

A spring 191 around rod 189 reacts between bearing 190 and cross member183. This spring functions in the same manner as spring 48, to restrictmovement of the dampers under the influence of the expansion of bellows185 until a predetermined elevation above sea level is reached, such as,for example, 2,000 feet.

As seen in FIG. 20, several bellows and sets of rods as shown in FIG. 19may be used on long dampers, or single bellows and sets of rods may beused on shorter .ones, but their actions are the same.

From the foregoing it is apparent that the dampers 175, 176 may bemanually positioned by manual manipulation of rods 189, a head 193 beingon each rod for that purpose, and the dampers may be locked inthatposition by set screws 192. When the set screws 192 are loosened themovement of the dampers is automatic, to provide an increase in thevolumetric capacities of the conduits at elevations above apredetermined elevation as the atmospheric air becomes more rarified.

' In FIG. 21 the damper elements 195, 196 are in the form ofhorizontally elongated blades extending horizontally between the ends ofa compartment, the damper 195 being in conduit 15 and damper 196 beingin conduit 16.

Damper element 195 is secured along its longitudinally extending edgefacing air flow to a horizontally extending shaft 197 that isjournalized for rotation at its ends in bearings carried by the endwalls of the compartment. Shaft 198 similarly supports the damperelement 196 in conduit 16. One of the ends of shafts 197, 198 projectoutwardly of one of the end walls 199 of the compartment and arm 200 issecured to the projecting end of shaft 197 while a corresponding arm 201is secured to the projecting end of shaft 198.

The outer ends of said arms are each slotted longitudinally thereof at202 and a horizontally extending rod 203 extends transversely across theslots A sleeve 205 adjustable on rod 203 longitudinally of the lattercarries a pin 204 that extends through the slot 202 in arm 200. A sleeve205' adjustable om rod 203 longitudinally of the latter carries a pin204 that extends into 8 slat 202 in arm 200. A set screw 207 lockssleeve 205 to rod 203 in adjusted position of the sleeve on the rod anda set screw 207 similarly locks sleeve 205' in adjusted position on rod203.

A bearing 208 between arms 200, 201 slidably supports rod 203 forhorizontal reciprocable movement and one end of rod 203 is connectedwith a plate 209 on one end of bellows 210 that is carried on a bracket211 secured to a wall of the display cabinet. Posts 212 on bracket 211slidably support plate 209.

A collar 213 is adjustably secured on rod 203 between bearing 208 andarm 201 by a screw 214, and a spring 215 around rod 203 reacts betweenthe bearing 208 and collar 213.

By the arrangement shown in FIG. 21, the walls separating the conduitsare not recessed and the barometric actuating means for the damperiswithin the confines of the outwardly projected outline of an end of thecabinet, where they may be readily accessible.

The positions of the dampers may be adjusted relative to each other byadjusting sleeve 205 or 205' on rod 203 and the dampers may be locked inposition in the conduits by set screw 216 in bearing 208. Also thedampers may be manually set by manipulating the head 217 on the end ofrod 203 that is remote from the bellows.

Where independently actuated dampers are in conduits 15, 16, the problemof adjusting their positions relative to each other in the respectiveconduits is simple. In FIGS. 19-21 where a single bellows is adapted toactuate the dampers in both conduits, it is to be understood that thedamper 176 in the outer conduit of the pair may be positioned to offer agreater percentage of resistance to the air in conduit 16 than thedamper offers to the air in conduit 15. Provision for this differencehas been made as herebefore described.

In a compartment under refrigeration, the primary air stream is the onethat carries the refrigeration effect from the coil system. As slightleakage occurs across the layer of guard air at the curtain, somemoisture passes to the primary air and is collected as frost on therefrigeration coils in the primary air circuit. This frosting and icingof the coils adds restriction to the air flow resulting in reducedvelocity of the primary air. If the primary air is operated at atemperature which does not cause frosting, the restriction is reduced,but a coil which is merely dehumidifying has a resistance ofapproximately 30 to 40 percent over a dry coil in ordinary airconditioning. Thus, unfrozen moisture with an unrestricted coil mayresult in a decreased velocity of the primary air.

In the present instance sensors of an electrical thermal anemometer Rand R FIGS. 2, 3, are respectively positioned in the primary air streamin conduit 15, and in the guard air stream in conduit 16. These sensorsare in a wheatstone bridge generally designated 54 (FIG. 3), the sensorsbeing of the resistance-bulb type. Variation in the velocity of airpassing over the resistance bulb will cause a variation in itsresistance, a decreasing velocity being reflected in an increasedresistance and vice versa.

purposes of adjustment and calibration. R and v R are connected inseries to form the resistance in the lower lefthand side of the bridge.

R is an adjustable resistance and is in series with R to form theresistance in the upper lefthand side of the bridge. The symbols P and Gindicate primary and guard air positions for the bulbs.

It should be realized that there is some variation in the resistance inthe bulbs R and R but this may be cared for at the time adjustment ismade.

A damper 55 in conduit 15 is connected by suitable linkage 56 with adamper actuating motor 57 which motor, in turn, may be controlled by amanual manipulation of a conventional remote potentiometer controller57' for positioning damper 55 for the desired velocity of the primaryair, although there are instances where a fine adjustment is notessential.

Once the velocity of the primary air has been established, R plus R willbe a general control resistance, and balance in the wheatstone bridgecircuit must be achieved by variation of the air flow in the guardconduit until the resistance of R plus R equals the resistance of R plusR Assuming the guard air is moving faster than the primary air, theresistance R will be relatively low, thus an imbalance will occurbetween points A, B of the wheatstone bridge. This imbalance in thebridge will be transmitted to a conventional electronic amplifier andcontroller 59. The unbalanced output from the wheatstone bridge isamplified electronically to actuate a solenoid switch in the controller59 which causes the reversible motor 60 connected with damper 61 in theguard air conduit to throttle until the resistance in R buildssufficiently to balance the wheatstone bridge. I

If the velocity of the guard air is less than that of the primary air, asignal of the opposite direction will occur, which, when amplified, willcause a second solenoid switching device in the controller 59 foractuating motor 60 in an opposite direction for moving the damper 61 toa more open position for balancing the velocity in the two conduits.

In FIG. 3, current is shown as being supplied from a DC source, which isthe simplest and preferred manner, although it is possible to operatethe wheatstone bridge with an AC current. The bridge must then beconstructed with correct resistances and inductances to balance thealternating bridge circuit. In the case of AC current, the impedance isthe total opposition offered by a circuit to the flow of current, itbeing the combined effect of the resistance and the reactance of a circuit.

The damper motors 57, 60 may be conventional 24 volt AC reversiblemotors withdual windings, and the transformers are normally included inthe controllers 57', 59. Said motors are geared motors-to move veryslowly, and motor 57 is the same type of motor as motor 59 except thatit would not be under the electronic control of the wheatstone bridgeoutput.

By increasing the resistance at R by the movement of slide wire 62, theresistance R R is increased thereby increasing the resistance in theprimary control circuit, which would have the same effect as a decreasein the velocity of the air over sensor R Thus damper 61 must be moved toreduce the velocity in conduit 16, thereby resulting in an increasedresistance in R to balance thev bridge. The decreased velocity effect onbulb R actually offsets the effect of adjusting the slide wire 62.

It is accordingly seen that, to reduce the guard air velocity in conduit16, add resistance at R and to increase the air velocity in'conduit l6,reduce the resistance at R The velocity of the primary air at thedischarge nozzle 17 is established by measurement with a proper velocityanemometer. With air in the primary and guard air conduits at differenttemperatures, the temperature effect for differential resistance betweenR and RP may be adjusted by R or R until the guard air is flowing at thesame velocity as the primary air.

Thereafter the guard air will track the primary air for equal velocity,or for differential velocity if so set.

Differential velocity between the guard and primary air results in amixing of the air of curtainsl9, 20 (FIG. 2) which increases therefrigeration load.

The electronic amplifiers and controllers used for ordinary airconditioning are readily adaptable for the type of signal received fromthe wheatstone bridge and the dampers are also conventional.

It is obvious that the system will operate when the primary air isheated and with the compartment under heating rather than refrigeration.

During operation of the system, there-are conditions in which moisturewill condense on the inner ceiling wall 2 and ice will form. Whendefrosted, this moisture may drop onto the products within thecompartment.

To overcome this objection, the upper inner wall 2 is inclineddownwardly from the nozzles at a slant sufficient to cause the moistureto flow rearwardly by gravity, and a horizontally extending trough 67 isremovably positioned at the upper rear corner to receive the water. Thebottom of the trough is inclined downwardly to one or more drain pipes68 that, in turn, extend downwardly across duct 15 and to rear wall 11,and then in conduit 16 to the lower end of the latter and through thebottom of the compartment.

A solenoid actuated valve 69 in drain pipe 68 adjacent its lower end isautomatically opened when the system is defrosted, and closed afterdefrosting, while a goose-neck trap 70 between valve 69 and outside thecompartment prevents ingress of air when valve 69 is open. As many drainpipes may be provided as are found to be necessary. A heating element 71may be in the bottom of trough 67 actuatable upon defrosting the systemto melt ice in the trough.

As an alternative, a trough 72 (FIG. 4) may be removably positioned inthe same place as trough 67. This trough is supported on a shelf 73 fromwhich it is readily removable when containing ice, and replaced by anempty trough.

In the modified form of the invention shown in FIG. 5, the same numeralswill be used to identify the structure that is the same as in FIG. 2.

Instead of using air movers 24, 25, conventional tangential air movers80, 81 are respectively positioned within conduits l5, 16 at thejunctures between the upper and rear walls defining the uppersubstantially right angle turns of the conduits (FIG. 5). Tangentialblowers are sometimes called right angle blowers, each comprising anannular row of horizontally elongated blades 82 (FIG. 6) that may extendapproximately the full width of each section. The blades of each blowerare supported around a shaft 83 that, in turn, is driven by a motor 845connected with one end of each shaft. Thus a plurality of said blowersin axial alignment, with one or more in the conduits of each section maybe driven by a motor positioned outside of one end of the section or byone interposed between axially aligned blowers in adjacent sections. Theair in the conduit is driven around an arcuate path around the corner ineach conduit from the inlet side to the outlet side and to nozzles 17,18. If desired, conduit 16 may be tapped for cooling air conducted tothe motors for cooling the latter, in a manner later illustrated.

FIG. 7 diagrammatically shows the arrangement in which a pair of coaxialtangential blowersare in an adjacent pair of sections in a cabinet. Theprimary and guard air in each section is moved by one of said coaxialpairs, requiring only one motor for the blowers of both pairs.

One of the adjacent sections is generally designated 91, and the other92, similar sections are indicated in FIG. 1. The primary air conduit ineach section is designated 93 (FIG. 7), and the guard air conduit 94. Avertical partition wall 95 in the upper corner of the primary airconduit 93 divides the conduits. Walls 96, 97 (FIG. 8) spaced from thecorner at opposite sides thereof extend from the partition 95 to one ofthe end walls of the section and across approximately half of theprimary air conduit in the section.

A horizontally-extending tangential blower 98 is sup ported for rotationabout its longitudinal axis in suitable bearings in the corner portionof the primary air conduit between the walls 96, 97. An opening 99 (FIG.8) is formed in the intermediate insulated wall 7' of the section abovethe wall 96 and adjacent to the lower side of blower 98, and a wall 100extends across the guard air conduit 94 along the upper edge of saidopening. This wall 100 extends from end-to-end of the section, hance allof the guard air is directed through opening 99 to the blower 98.

The same numerals are used to identify the walls of the conduits andother structure common to the different examples in FIGS. -10 exceptthat they may be primed.

The wall 97 at the other end of the partition 95 is in the upper,generally horizontally-extending, portion of the primary or inner airconduit and is spaced in said portion from the blower. An opening 101 inthe upper portion of the intermediate wall 7 opens into the mainunpartitioned length of conduit 94 for movement of the guard air to thedischarge nozzle 18.

From this it is seen that the guard air ascending the guard air conduit94' will all pass through opening 99 to the tangential blower 98 andwill be driven into the upper portion of conduit to the nozzle 18, thepartition 95 terminating at its ends adjacent the upper corner so thatthe movement of the air delivered to and discharged from the conduit 93will only be restricted at the upper corner of each compartment.

The second tangential blower 102 (FIGS. 7, 9) is coaxial with blower 98and is preferably on the same shaft. This blower extends across theportion of the primary air conduit 93 that is not blocked by wall 96(FIG. 9).

As illustrated in FIG. 7, a motor 105 may drive all of the coaxiallyaligned blowers in the pair of sections at opposite sides-of the motor,the walls 106 adjacent sections at opposite sides of the motor providinga space for the motor that is isolated from the conduits except forducts 107 and 108 that are tapped into the portions of the guard airconduit at the outlet side of the guard air conduit to conduct and movecooling air across the motor,'and ducts 109, 110 return the air to theguard air conduits at the inlet side of the blowers. This insures aconstant cooling of the motors by the guard air where as heretofore themotors for driving the primary air were positioned within the primaryair duct, thereby increasing the cost of cooling the compartments.

The inner wall 1 of the compartments, or sections, are preferably heatinsulated along portion 112 (FIG. 8) in which each blower 98 ispositioned to reduce transfer of heat from the guard air to the interiorof the compartment, although any cooling of the guard air at the corner,by conduction, from the primary air, will function to cool the motor105.

Diagonally extending rows of horizontally extending, transverselycurved, turning vanes 113 (FIG. 8) extend across the portion 1 14 of theguard air conduit between the inlet 99 and outlet 101, and at the inletand outlet, to guide the air past the turns to and from blower 98.

In the foregoing arrangement, the motor will rotate all of the axiallyaligned blowers in the same direction, and one motor will take the placeof several propellet type fans where a motor-driven fan is in eachsection.

In certain instances it may be desirable to simplify the relativelytortuous passage of air in the portion 114 of the guard air conduit asshown in FIG. 8.

FIGS. 10, 11, 12 illustrate one arrangement for accomplishing thisresult and FIG. 9, 10, 11 show another. In each example the blower andconduit arrangement is the same as shown in FIG. 10, 11.

In FIG. 10 one section is shown in which coaxial, tangential blowers122, 123 are used, the blower 122 being for guard air and the blower 123for primary air.

In this instance in the primary air conduit, spaced opposed partitions124 (FIG. 10) provide a space 125 between the blowers 122, 123 in whichmotor 126 is positioned and which is connected by a pair of'conventionaldrive chains, belts or gears with the shafts of blowers 122, 123respectively to rotate the blowers in opposite directions. Walls 127,128 extendingrespectively approximately at right angles to the rearouter wall 11' and from the upper outer wall 10' at the upper corner(FIGS. 11, 12) to meeting relation closing the guard air conduit at thecorner. An inlet opening 130 in the intermediate wall 7 below wall 130at the side of the partition in which blower 122 is positioned passesthe guard air to blower 122. Outlet opening 131 in intermediate wall 6'is above blower 122 at the same side of partition 124 as walls 127, 128and the blower 122 is in the same position as blower 123.

By this structure only one pair of turns at vanes 135 is requiredinstead of the four shown in FIG. 8, but the blowers rotate in oppositedirections.

The guard air conduit is tapped at the discharge side of the blower by aduct 138 to provide cooling air to motor 126, and a duct 137 conductsthe cooling air back into the conduit 94 at the inlet side of theblower.

FIG. 13 shows the same corner arrangement for the blowers, except that asingle partition 139 is used, and motors 140, 141 are respectivelyconnected with the blowers 143, 142 that are respectively at oppositesides of the partition, one motor driving the blower 143 in the samedirection as blower 123 is driven, while the motor 141 drives the blower142 in conduit 94 in the same direction as blower 122. In thisarrangement a duct system 144 taps the guard air conduit to delivercooling air from the guard air conduit to motors 140 and 141 for coolingthe latter, while a duct 145 returns the air to the inlet side of blower142.

While the preferred form would employ a separate motor for the blowersin the primary and guard air conduits, without dividing the conduits anddiverting the air in one conduit, as disclosed in FIG. 6 the arrangementshown in FIGS. 7-12 has advantages over conventional systems in someinstances. Also, the air flow control and dehumidifier in the guard airstream, and other structural features, are improvements in any airmoving arrangement.

In the modifications shown in FIGS. 14-18, the flow control anddehydrating means employed in FIGS. 2-4 may remain the same, includingthe employment of the separate primary air and guard air conduits andtheir separate discharge nozzles and intake openings.

Within the top part of the cabinet the intermediate wall 145 between theprimary air conduit 146 and the guard air conduit 147 is formed with agap within which motor 148 and blower 149 are positioned, the blower inthis instance being the propeller fan type with the blades adapted toextend across the distance between the outermost and innermost upperwalls of the cabinet, and guide walls may extend convergently from theend walls of the compartment toward the blower to guide the air in bothconduits to the blower fan for movement therepast.

Cooling coils 150 positioned within the upper portion of the primary airconduit 146 between the fan 149 and the discharge nozzle 151 cool theprimary air that is discharged to form the inner layer of the aircurtain, while the guard air is discharged from nozzle 152.

In FIG. 15, at the intake side of the fan and at the opposite dischargeside, the latter being the side toward the discharge nozzles, a pair ofgenerally horizontallydisposed plates 154, 155 are positioned, the plate154 being at the intake side of the blower and the plate 155 being atthe-discharge side.

These plates are horizontal extensions of the intermediate wall betweenthe primary and guard air conduits, and extend to opposite sides of thefan or blower 149.

In FIG. 16, plates 156, 157 are similar to plates 154, 155 with plate156 disposed horizontally (FIG.16), and while the plate 157 at thedischarge side of the blower may have its edge 158 that is remote fromthe blower also horizontal, the plate is twisted about an extension ofthe axis of the fan so the edge 159 adjacent the blower is tilted in thedirection of rotation of the blades of the fan. Thus at one side of theaxis, edge 159 extends below the plane in which edge 158 is positioned,while the edge 159 at the other side of the axis is above said plane.

In FIG. 17 plates 160, 161 similar to plates 156, 157 are shown at theinlet and discharge sides of the fan, but in this case the plate 160 atthe inlet side has the edge 162 remote from the fan horizontal, and theedge 163 adjacent the fan tilted oppositely to the direction of movementof the fan blades, while plate 161 is horizontal.

In FIG. 18, plate 164 at the inlet side of the fan is in the sameposition of plate 160 while plate 165 at the discharge side is in theposition of plate 157.

The results in each instance are similar and directed to the same end ofstraightening the tendency of the body of air to swirl in the directionof rotation of the fan after leaving the fan.

It is to be understood that the cooling coil 150 may be positioned inthe rear or bottom portion of conduit 146 and that the position of thefan or blower 149 is not restricted to the upper portions of conduits146, 1417.

We claim:

1. The method of temperature conditioning air within a predeterminedenclosed area having an access opening in one side but otherwiseenclosed, comprising the steps of:

a. circulating in the same direction an inner and outer layer of airrespectively in adjacent, parallel, endless inner and outer pathsextending around said area and across said opening with said inner layeradjacent said area and the outer layer outwardly thereof relative tosaid area with said inner and outer paths and the air therein separatedfrom each other along the lengths extending to and from said opening andwith the portion of the inner layer extending across said opening inengagement with the air within said area and with the portion of theouter layer adjacent thereto, whereby said portions provide adjacentcurtains extending between the ambient air and the air within said area;

b. temperature conditioning the air of said inner layer to a temperaturedifferent from that of said ambient air whereby air within said areawill be similarly conditioned and said portion of said outer layer willguard said inner layer against intrusion by said ambient air;

c. applying a constant, uniform moving force to the air in said innerand outer paths for circulating them in said paths in the same directionwith said inner and outer paths each having a predetermined volumetriccapacity for producing predetermined distribution pressures at thepoints of discharge of said inner layer and said outer layer from saidinner and outer paths across said opening when said area is at sealevel;

d. increasing the volumeric capacity of said inner path upon apredetermined increase in the rarity of the atmosphere at higherelevations for maintaining an efficient distribution pressure at saidhigher elevations at said uniform'moving force.

2. In the method as defined in claim 1:

e. controlling the volumeric capacities of said inner and outer paths atdifferent predetermined elevations of said area above sea level withoutchanging said uniform force by sufficiency increasing the volumericcapacities of said paths to flow of air therethrough to maintainefficient distribution pressure at said outlets.

3. In the method as defined in claim 2:

f. said step of increasing the volumeric capacities of said paths beingeffected by enlargement of said paths to passage of air therethroughunder the in fluence of the expansive force of a gas enclosed at sealevel.

4. The method of temperature conditioning air within a predeterminedenclosed area having an access opening in one side but otherwiseenclosed, comprising the steps of:

a. circulation in the same direction an inner and outer layer of airrespectively in adjacent, parallel, endless inner and outer pathsextending around said area and across said opening with said inner layeradjacent said area and the outer layer outwardly thereof relative tosaid area with said inner and outer paths and the air therein separatedfrom each other along the lengths extending to and from said opening andwith the portion of the inner layer extending across said opening inengagement with the air within said area and with the portion of theouter layer adjacent thereto, whereby said portions provide adjacentcurtains extending between the ambient air and the air within said area;

b. temperature conditioning the air of said inner layer to a temperaturedifferent from that of said ambient air whereby air within said areawill be similarly conditioned and said portion of said outer layer willguard said inner layer against intrusion by said ambient air;

c. the conditioning of said air being by refrigeration thereof withinsaid path prior to the formation of said curtain;

d. controlling the velocity of the air in said inner and outer pathsextending to said curtain relative to each other to provide apredetermined velocity within each path by developing within each pathforces responsive to changes from said predetermined velocity andapplying said forces to oppositely movable path restrictors in saidpaths restricting or opening said paths effecting restoration to saidpredetermined velocity of air in said inner and outer passagewayaccording to character of the variation.

5. An apparatus for conditioning a body of air within an enclosed areaprovided with an access opening in one side for insertion of objectstherethrough into said area from ambient atmospheric air outside saidarea for withdrawal therefrom, said apparatus including an inner and anouter conduit extending around said area terminating in a dischargeoutlet along one edge of said opening and an inlet along the oppositeedge facing said discharge outlet, said inner conduit having anuninsulated wall of heat transfer material in heat transfer relation tothe air within said area, and said outer conduit being adjacent andoutwardly of said inner conduit relative to said area:

a. air moving means for simultaneously circulating air in inner andouter endless paths extending through said inner and outer conduits andacross said opening from said discharge outlets to said inlets,providing a curtain of air across said opening in the form of inner andouter layers respectively in continuation of the air of said inner andouter conduit;

b. air cooling means for cooling the air moving through said innerconduit for cooling the air within said area through conduction throughsaid uninsulated wall; and v c. control means for automaticallycontrolling the velocity of the air in said paths at predeterminedvelocities independently of said air moving means.

6. In an apparatus as defined in claim d. said control means beingvelocity-responsive electrical resistance elements respectivelypositioned within said conduits and velocity controlling dampers in anelectrical circuit with said elements respectively supported within eachconduit and operatively connected with electrically actuated means formoving said dampers to positions to automatically effect restoration ofthe desired predetermined velocities upon variations therefrom occurringin said conduits.

7. In apparatus as defined in claim 5:

d. heat transfer means within said inner conduit in heat exchangerelation with the cold air in said inner conduit extending into saidouter conduit in heat exchange relation with the air in said outerconduit for dehydrating the air in said outer conduit.

8. In apparatus as defined in claim 5:

(1. pressure control means within at least one of said conduits movableto different positions therein for varying the distribution pressure ofair at its discharge nozzle.

9. In apparatus as defined in claim 5:

d. pressure control means respectively within said inner path and saidouter path movable todifferent positions therein for varying thedistribution pressure in said inner and outer conduits at theirdischarge outlets upon a predetermined increase in the rarity of theatmospheric air at different elevations above sea level, wherebyefficient distribution pressures at said outlets will be maintained atsaid predetermined elevations.

10. In apparatus -as defined in claim 9:

e. said pressure control means including an expandable member enclosinga body of gas expandable at said predetermined altitudes, and meanswithin said conduits restricting passage of air through said conduits toa predetermined volumeric amount connected with said expandable memberfor movement to less restrictive positions for increasing the volumericcapacities of said paths to passage of air therethrough for therebymaintaining efficient distribution pressures of air at said outlets.

11. An apparatus for conditioning a body of air within an enclosed areaprovided with an access opening in one side for insertion of objectstherethrough into said area from ambient atmospheric air outside saidarea and for withdrawal therefrom, said apparatus including an inner andan outer conduit extending around said area terminating in a dischargeoutlet along one edge of said opening and an inletalong the oppositeedge facing said discharge outlet, said inner conduit having anuninsulated wall of heat transfer material in heat transfer relation tothe air within said area, and said outer conduit being adjacent andoutwardly of said inner conduit relative to said area:

a. air moving means for simultaneously circulating air in inner andouter endless paths extending through said inner and outer conduits andacross said opening from said discharge outlets to said inlets,providing a curtain of air across said opening in the form of inner andouter layers respectively in continuation of the air of said inner andouter conduit;

b. air cooling means for cooling the air moving through said innerconduit for cooling the air within said area through conduction throughsaid uninsulated wall;

c. dehydrating means positioned within said outer conduit fordehydrating the air moving therein to said discharge outlets;

d. said dehydrating means comprising heat transfer means in heatexchange relation with the air in said inner conduit extending into saidouter conduit in heat exchange relative with the air in the latter.

12. In apparatus as defined in claim 11:

e. a wall of heat insulating material defining a wall common to andseparating said inner conduit from said outer conduit;

f. said heat transfer means including a plate of heat transfer materialwithin said inner conduit in spaced opposed relation to side of saidinner conduit in heat exchange relation to the air within said areaproviding a reflective space between said plate and said side of saidinner conduit, and heat exchange members integral with said plateextending into said outer conduit for passage of the air within thelatter therepast and condensation of moisture in said last mentionedair.

13. An apparatus for conditioning a body of air within an enclosed areaprovided with an access opening in one side forinsertion of objectstherethrough into said area from ambient atmospheric air outside saidarea and for withdrawal therefrom, said apparatus including an inner andan outer conduit extending around said area terminating in a dischargeoutlet along one edge of said opening and an inlet along the oppositeedge facing said discharge outlet, said inner conduit having anuninsulated wall of heat transfer material in heat transfer relation tothe air within said area, and said outer conduit being adjacent andoutwardly of said inner conduit relative to said area:

a. air moving means for simultaneously circulating the air in inner andouter endless paths extending through said inner and outer conduits andacross said opening from said discharge outlets to said inlets,providing a curtain of air across said opening in the form of inner andouter layers respectively in continuation of the air of said inner andouter conduit;

b. air cooling means for cooling the air moving through said innerconduit for cooling the air within said area through conduction throughsaid uninsulated wall;

c. control means for automatically controlling the velocity of the airin said paths at predetermined velocities independently of said airmoving means; and

d. pressure control means respectively within said inner path and saidouter path movable to different positions therein for varying thedistribution pressure in said inner and outer conduits at theirdischarge outlets upon a predetermined increase in the rarity of theatmospheric air at different elevations above sea level, wherebyefficient distribution pressures at said outlets will be maintained atsaid predetermined elevations.

14; An apparatus for conditioning a body of air within an enclosed areaprovided with an access opening in one side for insertion of objectstherethrough into said area from ambient atmospheric air outside saidarea and for withdrawal therefrom, said apparatus including an inner andan outer conduit extending around said area terminating in a dischargeoutlet along one edge of said opening and an inlet along the oppositeedge facing said discharge outlet, said inner conduit having anuninsulated wall of heat transfer material in heat transfer relation tothe air within said area, and said outer conduit being adjacent ,andoutwardly of said inner conduit relative to said area:

a. air moving means for simultaneously circulating air in inner andouter endless paths extending through said inner and outer conduits andacross said opening from said discharge outlets to said inlets,providing a curtain of air across said opening in the form of inner andouter layers respectively in continuation of the air of said inner andouter conduit;

b. air cooling means for cooling the air moving through said innerconduit for cooling the air within said area through conduction throughsaid uninsulated wall;

c. pressure control means respectively within said inner path and saidouter path movable to different positions therein for varying thedistribution pressure in said inner and outer conduits at theirdischarge outlets upon a predetermined increase in the rarity of theatmospheric air at different elevations above sea level, wherebyefficient distribution pressures at said outlets will be maintained atsaid predetermined elevations;

(1. said pressure control means including an expandable member enclosinga body of gas expandable at said predetermined altitudes, and meanswithin said conduits restricting passage of air through said conduits toa predetermined volumetric amount connected with said expandable memberfor movement to less restrictive positions for increasing the volumetriccapacities of said paths to passage of air therethrough for therebymaintaining efficient distribution pressures of air at said outlets.

15. The method of temperature conditioning air within a predeterminedenclosed area having an access opening in one side but otherwiseenclosed, comprising the steps of:

a. circulation in the same direction an inner and outer layer of airrespectively in adjacent, parallel, endless inner and outer pathsextending around said area and across said opening with said inner layeradjacent said area and the outer layer outwardly thereof relative tosaid area with said inner and outer paths and the air therein separatedfrom each other along the lengths extending to and from said opening andwith the portion of the inner layer extending across said opening inengagement with the air within said area and with the portion of theouter layer adjacent thereto, whereby said portions provide adjacentcurtains extending between the ambient air and the air within said area;

b. temperature conditioning the air of said inner layer to a temperaturedifferent from that of said ambient air whereby air within said areawill be similarly conditioned and said portion of said outer layer willguard said inner layer against intrusion by said ambient air; 7

c. the conditioning of said air being by refrigeration thereof withinsaid path prior to the formation of said curtain;

d. removing moisture from the air of said outer layer by moving itacross a heat conductor between said inner and outer paths in heatexchange relation with the air in both paths at a restricted locationtherealong for condensing excess moisture in the air of said outer layerat said location.

16. In the method as defined in claim 19:

e. varying the degree of cooling of the air in said outer path at saidlocation by varying the position of said heat conductor toward and awayfrom the side of the inner path opposite thereto, thereby varying theconductance of the space between said heat conductor and said lastmentioned side of said path.

17. In a refrigerated display compartment having a ceiling wall bottomwall, opposed lateral walls and a vertically extending rear walldefining the bounds of a storage space for products, and an accessopening at the front opposite said rear wall for insertion and removalof such products into and out of said space:

a. a continuous inner conduit for air extending across said ceiling,rear and bottom walls with said walls being uninsulated and forming oneside of said c. said conduits having an intermediate wall common to bothconduits spaced outwardly of said ceiling, bottom and rear wall havingterminal ends at said inlet openings and said outlet openings;

refrigerating means within said inner conduit for inner conduit, and anouter continuous conduit for air coextensive with said inner conduitadjoining and positioned outwardly of said inner conduit relative tosaid storage space, said inner and outer cooling the air movingtherethrough to said outlets, and a single motor-driven, propeller,fan-type blower having blades extending across said inner and outerconduits between opposite terminal ends gtgigggjg? 5532125 23? zg gzsgfii ggzgf of the latter for simultaneously moving the air in 'd 't f th irinlet nin s to th ir utings at their opposite ends at the side of saidaccess conflul i and e in opening opposite said one side of the latterwith oPemngS 9 ormmg Sm l ag Said outlet openings facing Said inletopenings to said intermediate wall for rotation of said blades lllprovide an inner and outer curtain of air flowing a planehnormal to thelengths of smd l across said access opening, from said outlet openfdlsplay f l defined P clam ings to Said inlet openings upon movement ofair in e. said intermediate wall including a portion thereof saidconduits from said inlet openings to said outlet adJasent one of theSides 531d blower Supported openings; in a position for counteractingthe tendency of the b. a discharge nozzle in the outlet of h d it 20 airmoved by said blades to said discharge nozzles having means within eachfor directin the air di to swirl in the direction of rotation of saidblades charge therefrom in contiguous curtains extending after leavingthe latter. 7 from said nozzles to said inlet openings;

1. The method of temperature conditioning air within a predeterminedenclosed area having an access opening in one side but otherwiseenclosed, comprising the steps of: a. circulating in the same directionan inner and outer layer of air respectively in adjacent, parallel,endless inner and outer paths extending around said area and across saidopening with said inner layer adjacent said area and the outer layeroutwardly thereof relative to said area with said inner and outer pathsand the air therein separated from each other along the lengthsextending to and from said opening and with the portion of the innerlayer extending across said opening in engagement with the air withinsaid area and with the portion of the outer layer adjacent thereto,whereby said portions provide adjacent curtains extending between theambient air and the air within said area; b. temperature conditioningthe air of said inner layer to a temperature different from that of saidambient air whereby air within said area will be similarly conditionedand said portion of said outer layer will guard said inner layer againstintrusion by said ambient air; c. applying a constant, uniform movingforce to the air in said inner and outer paths for circulating them insaid paths in the same direction with said inner and outer paths eachhaving a predetermined volumetric capacity for producing predetermineddistribution pressures at the points of discharge of said inner layerand said outer layer from said inner and outer paths across said openingwhen said area is at sea level; d. increasing the volumeric capacity ofsaid inner path upon a predetermined increase in the rarity of theatmosphere at higher elevations for maintaining an efficientdistribution pressure at said higher elevations at said uniform movingforce.
 2. In the method as defined in claim 1: e. controlling thevolumeric capacities of said inner and outer paths at differentpredetermined elevations of said area above sea level without changingsaid uniform force by sufficiency increasing the volumeric capacities ofsaid paths to flow of air therethrough to maintain efficientdistribution pressure at said outlets.
 3. In the method as defined inclaim 2: f. said step of increasing the volumeric capacities of saidpaths being effected by enlargement of said paths to passage of airtherethrough under the influence of the expansive force of a gasenclosed at sea level.
 4. The method of temperature conditioning airwithin a predetermined enclosed area having an access opening in oneside but otherwise enclosed, comprising the steps of: a. circulation inthe same direction an inner and outer layer of air respectively inadjacent, parallel, endless inner and outer paths extending around saidarea and across said opening with said inner layer adjacent said areaand the outer layer outwardly thereof relative to said area with saidinner and outer paths and the air therein separated from each otheralong the lengths extending to and from said opening and with theportion of the inner layer extending across said opening in engagementwith the air within said area and with the portion of the outer layeradjacent thereto, whereby said portions provide adjacent curtainsextending between the ambient air and the air within said area; b.temperature conditioning the air of said inner layer to a temperaturedifferent from that of said ambient air whereby air within said areawill be similarly conditioned and said portion of said outer layer willguard said inner layer against intrusion by said ambient air; c. theconditioning of said air being by refrigeration thereof within said pathprior to the formation of said curtain; d. controlling the velocity ofthe air in said inner and outer paths extending to said curtain relativeto each other to provide a predetermined velocity within each path bydeveloping within each path forces responsive to changes from saidpredetermined velocity and applying said forces to oppositely movablepath restrictors in said paths restricting or opening said pathseffecting restoration to said predetermined velocity of air in saidinner and outer passageway according to character of the variation. 5.An apparatus for conditioning a body of air within an enclosed areaprovided with an access opening in one side for insertion of objectstherethrough into said area from ambient atmospheric air outside saidarea for withdrawal therefrom, said apparatus including an inner and anouter conduit extending around said area terminating in a dischargeoutlet along one edge of said opening and an inlet along the oppositeedge facing said discharge outlet, said inner conduit having anuninsulated wall of heat transfer material in heat transfer relation tothe air within said area, and said outer conduit being adjacent andoutwardly of said inner conduit relative to said area: a. air movingmeans for simultaneously circulating air in inner and outer endlesspaths extending through said inner and outer conduits and across saidopening from said discharge outlets to said inlets, providing a curtainof air across said opening in the form of inner and outer layersrespectively in continuation of the air of said inner and outer conduit;b. air cooling means for cooling the air moving through said innerconduit for cooling the air within said area through conduction throughsaid uninsulated wall; and c. control means for automaticallycontrolling the velocity of the air in said paths at predeterminedvelocities independently of said air moving means.
 6. In an apparatus asdefined in claim 5: d. said control means being velocity-responsiveelectrical resistance elements respectively positioned within saidconduits and velocity controlling dampers in an electrical circuit withsaid elements respectively supported within each conduit and operativelyconnected with electrically actuated means for moving said dampers topositions to automatically effect restoration of the desiredpredetermined velocities upon variations therefrom occurring in saidconduits.
 7. In apparatus as defined in claim 5: d. heat transfer meanswithin said inner conduit in heat exchange relation with the cold air insaid inner conduit extending into said outer conduit in heat exchangerelation with the air in said outer conduit for dehydrating the air insaid outer conduit.
 8. In apparatus as defined in claim 5: D. pressurecontrol means within at least one of said conduits movable to differentpositions therein for varying the distribution pressure of air at itsdischarge nozzle.
 9. In apparatus as defined in claim 5: d. pressurecontrol means respectively within said inner path and said outer pathmovable to different positions therein for varying the distributionpressure in said inner and outer conduits at their discharge outletsupon a predetermined increase in the rarity of the atmospheric air atdifferent elevations above sea level, whereby efficient distributionpressures at said outlets will be maintained at said predeterminedelevations.
 10. In apparatus as defined in claim 9: e. said pressurecontrol means including an expandable member enclosing a body of gasexpandable at said predetermined altitudes, and means within saidconduits restricting passage of air through said conduits to apredetermined volumeric amount connected with said expandable member formovement to less restrictive positions for increasing the volumericcapacities of said paths to passage of air therethrough for therebymaintaining efficient distribution pressures of air at said outlets. 11.An apparatus for conditioning a body of air within an enclosed areaprovided with an access opening in one side for insertion of objectstherethrough into said area from ambient atmospheric air outside saidarea and for withdrawal therefrom, said apparatus including an inner andan outer conduit extending around said area terminating in a dischargeoutlet along one edge of said opening and an inlet along the oppositeedge facing said discharge outlet, said inner conduit having anuninsulated wall of heat transfer material in heat transfer relation tothe air within said area, and said outer conduit being adjacent andoutwardly of said inner conduit relative to said area: a. air movingmeans for simultaneously circulating air in inner and outer endlesspaths extending through said inner and outer conduits and across saidopening from said discharge outlets to said inlets, providing a curtainof air across said opening in the form of inner and outer layersrespectively in continuation of the air of said inner and outer conduit;b. air cooling means for cooling the air moving through said innerconduit for cooling the air within said area through conduction throughsaid uninsulated wall; c. dehydrating means positioned within said outerconduit for dehydrating the air moving therein to said dischargeoutlets; d. said dehydrating means comprising heat transfer means inheat exchange relation with the air in said inner conduit extending intosaid outer conduit in heat exchange relative with the air in the latter.12. In apparatus as defined in claim 11: e. a wall of heat insulatingmaterial defining a wall common to and separating said inner conduitfrom said outer conduit; f. said heat transfer means including a plateof heat transfer material within said inner conduit in spaced opposedrelation to side of said inner conduit in heat exchange relation to theair within said area providing a reflective space between said plate andsaid side of said inner conduit, and heat exchange members integral withsaid plate extending into said outer conduit for passage of the airwithin the latter therepast and condensation of moisture in said lastmentioned air.
 13. An apparatus for conditioning a body of air within anenclosed area provided with an access opening in one side for insertionof objects therethrough into said area from ambient atmospheric airoutside said area and for withdrawal therefrom, said apparatus includingan inner and an outer conduit extending around said area terminating ina discharge outlet along one edge of said opening and an inlet along theopposite edge facing said discharge outlet, said inner conduit having anuninsulated wall of heat transfer material in heat transfer relation tothe air within said area, and said outer conduit being adjacenT andoutwardly of said inner conduit relative to said area: a. air movingmeans for simultaneously circulating the air in inner and outer endlesspaths extending through said inner and outer conduits and across saidopening from said discharge outlets to said inlets, providing a curtainof air across said opening in the form of inner and outer layersrespectively in continuation of the air of said inner and outer conduit;b. air cooling means for cooling the air moving through said innerconduit for cooling the air within said area through conduction throughsaid uninsulated wall; c. control means for automatically controllingthe velocity of the air in said paths at predetermined velocitiesindependently of said air moving means; and d. pressure control meansrespectively within said inner path and said outer path movable todifferent positions therein for varying the distribution pressure insaid inner and outer conduits at their discharge outlets upon apredetermined increase in the rarity of the atmospheric air at differentelevations above sea level, whereby efficient distribution pressures atsaid outlets will be maintained at said predetermined elevations.
 14. Anapparatus for conditioning a body of air within an enclosed areaprovided with an access opening in one side for insertion of objectstherethrough into said area from ambient atmospheric air outside saidarea and for withdrawal therefrom, said apparatus including an inner andan outer conduit extending around said area terminating in a dischargeoutlet along one edge of said opening and an inlet along the oppositeedge facing said discharge outlet, said inner conduit having anuninsulated wall of heat transfer material in heat transfer relation tothe air within said area, and said outer conduit being adjacent andoutwardly of said inner conduit relative to said area: a. air movingmeans for simultaneously circulating air in inner and outer endlesspaths extending through said inner and outer conduits and across saidopening from said discharge outlets to said inlets, providing a curtainof air across said opening in the form of inner and outer layersrespectively in continuation of the air of said inner and outer conduit;b. air cooling means for cooling the air moving through said innerconduit for cooling the air within said area through conduction throughsaid uninsulated wall; c. pressure control means respectively withinsaid inner path and said outer path movable to different positionstherein for varying the distribution pressure in said inner and outerconduits at their discharge outlets upon a predetermined increase in therarity of the atmospheric air at different elevations above sea level,whereby efficient distribution pressures at said outlets will bemaintained at said predetermined elevations; d. said pressure controlmeans including an expandable member enclosing a body of gas expandableat said predetermined altitudes, and means within said conduitsrestricting passage of air through said conduits to a predeterminedvolumetric amount connected with said expandable member for movement toless restrictive positions for increasing the volumetric capacities ofsaid paths to passage of air therethrough for thereby maintainingefficient distribution pressures of air at said outlets.
 15. The methodof temperature conditioning air within a predetermined enclosed areahaving an access opening in one side but otherwise enclosed, comprisingthe steps of: a. circulation in the same direction an inner and outerlayer of air respectively in adjacent, parallel, endless inner and outerpaths extending around said area and across said opening with said innerlayer adjacent said area and the outer layer outwardly thereof relativeto said area with said inner and outer paths and the air thereinseparated from each other along the lengths extending to and from saidopening and with the portion of the inner layer extending across saidopening in engagement witH the air within said area and with the portionof the outer layer adjacent thereto, whereby said portions provideadjacent curtains extending between the ambient air and the air withinsaid area; b. temperature conditioning the air of said inner layer to atemperature different from that of said ambient air whereby air withinsaid area will be similarly conditioned and said portion of said outerlayer will guard said inner layer against intrusion by said ambient air;c. the conditioning of said air being by refrigeration thereof withinsaid path prior to the formation of said curtain; d. removing moisturefrom the air of said outer layer by moving it across a heat conductorbetween said inner and outer paths in heat exchange relation with theair in both paths at a restricted location therealong for condensingexcess moisture in the air of said outer layer at said location.
 16. Inthe method as defined in claim 19: e. varying the degree of cooling ofthe air in said outer path at said location by varying the position ofsaid heat conductor toward and away from the side of the inner pathopposite thereto, thereby varying the conductance of the space betweensaid heat conductor and said last mentioned side of said path.
 17. In arefrigerated display compartment having a ceiling wall bottom wall,opposed lateral walls and a vertically extending rear wall defining thebounds of a storage space for products, and an access opening at thefront opposite said rear wall for insertion and removal of such productsinto and out of said space: a. a continuous inner conduit for airextending across said ceiling, rear and bottom walls with said wallsbeing uninsulated and forming one side of said inner conduit, and anouter continuous conduit for air coextensive with said inner conduitadjoining and positioned outwardly of said inner conduit relative tosaid storage space, said inner and outer conduits having outlet openingsat one of their ends at one side of said access opening, and inletopenings at their opposite ends at the side of said access openingopposite said one side of the latter with said outlet openings facingsaid inlet openings to provide an inner and outer curtain of air flowingacross said access opening, from said outlet openings to said inletopenings upon movement of air in said conduits from said inlet openingsto said outlet openings: b. a discharge nozzle in the outlet of eachconduit having means within each for directing the air dischargetherefrom in contiguous curtains extending from said nozzles to saidinlet openings; c. said conduits having an intermediate wall common toboth conduits spaced outwardly of said ceiling, bottom and rear wallhaving terminal ends at said inlet openings and said outlet openings;refrigerating means within said inner conduit for cooling the air movingtherethrough to said outlets, and a single motor-driven, propeller,fan-type blower having blades extending across said inner and outerconduits between opposite terminal ends of the latter for simultaneouslymoving the air in said conduits from their inlet openings to theiroutlet openings for forming said curtains, and a gap in saidintermediate wall for rotation of said blades in a plane normal to thelengths of said conduits.
 18. In a display compartment as defined inclaim 17: e. said intermediate wall including a portion thereof adjacentone of the sides of said blower supported in a position forcounteracting the tendency of the air moved by said blades to saiddischarge nozzles to swirl in the direction of rotation of said bladesafter leaving the latter.